EP4028206B1 - Internal welding of pipes and profiles - Google Patents

Description

The invention relates to a device and a method for the internal welding of pipes and profiles, comprising a cantilever arm which is attached to a suspension which can be inserted into the pipe or profile to be welded and on which a welding head is slidably attached, the cantilever arm further having a Includes laser and camera.

With internal welding, the welding head is usually located at the end of a long cantilever arm, which is inserted into the tube or profile. The media required for welding (gases, welding current, welding cable, welding powder, welding wire, ...) are fed through or along the cantilever arm to the welding head.

Such devices and methods are known, for example from U.S. 3,764,056 and the US 10,040,141 B2 .

The document U.S. 3,764,056 discloses an apparatus for welding pipes together from the inside of the pipe. In this case, a cantilever arm, at the tip of which a welding head is arranged, is pushed into the pipe so that the welding head is placed in the vicinity of the area to be welded, which is formed by the contact surface of the pipes joined together. The tubes rotate while the adjustable weld head creates the weld. With the help of a camera mounted near the welding head, the welding process can be observed visually and controlled remotely. The welding head can be positioned relative to the pipe during the welding process.

The document U.S. 10,040,141 describes a laser-controlled internal welding machine for a pipeline. The system includes an external Positioning device with which the pipe segments to be welded can be aligned relative to one another so that they can be welded with the internal welding machine. The welding apparatus also includes a laser for monitoring the weld profile and for guiding an articulation head of the weld head. A camera for visual inspection of the weld seam after the welding process is also available.

The use of a laser to record profiles is also from the CN 106705857A known. The CN 106705857A deals with the surveying of surfaces using a laser system in the field of building geology, namely subsoil and tunnel technology. To do this, a laser placed on the surface to be measured is directed at a fixed plate. If the laser is moved along the surface, or if the surface shifts when the laser is fixed, the point of light generated by the laser beam on the plate changes or shifts accordingly. From the displacement of the point of light on the plate, conclusions can then be drawn about the structure of the surface.

However, the internal welding machines described have a number of fundamental problems: During the welding process, a magnetic field is created which deflects and/or twists the cantilever arm. The extent of this deflection and/or torsion depends on how far the cantilever arm was inserted into the pipe or profile to be welded. In addition, the welding process itself and the transport of the welding media to the welding head - especially when welding "under powder"; the welding flux is typically at 120°C and the welding cables can reach 100°C - high temperatures that cause additional change in deflection and twisting of the cantilever. Twisting is also caused, for example, by the fact that the hot welding powder is usually only transported on one side of the cantilever and that the welding cables do not all have the same temperature due to different current loads. At large lengths of the cantilever, even small temperature differences between left/right/above/below can cause large deflections at the end of the cantilever/weld head.

This three-dimensional torsion, deflection or deflection of the cantilever arm caused by magnetism and the effects of heat leads to a corresponding change in the position of the welding head, which is no longer in the desired position, which has a negative effect on the welding process and the weld seam geometry, and thus the weld seam quality , affects.

Here the invention wants to create an improvement.

This object is achieved according to the invention in that a device of the type mentioned at the outset has a control device for moving the welding head, one or more lasers are attached to the suspension, one or more cameras are attached to the welding head, one or more laser beams respectively the one or more cameras are directed and recognizable by them, an evaluation module is present, which can evaluate changes in the relative positions of the laser beams recognized by the one or more cameras, generate a signal from this and feed this to the control device for shifting the welding head.

The subject of the invention is therefore a device according to claim 1.

According to the invention, a pipe can also be a tubular element, also elliptical, a profile, for example, a U-shaped or a rectangular profile.

• erfassen von Ausgangswerten X, Y der Position des oder jeden Laserstrahls mit der oder jeder Kamera bei einem Ausgangszustand der Vorrichtung,
• erfassen von Abweichungen dX, dY der Position des oder jeden Laserstrahls von den Ausgangswerten X, Y während des Betriebs der Vorrichtung,
• erzeugen eines Signals für die Steuereinrichtung aus den erfaßten Abweichungen dX, dY,
• weiterleiten des Signals an die Steuereinrichtung, welche den Schweißkopf auf Basis des Signals so verschiebt, daß die Abweichungen dX, dY kleiner werden.

The invention also relates to a method for moving a welding head in a device according to one or more of claims 1 to 7, comprising at least the following steps:

• detecting initial values X, Y of the position of the or each laser beam with the or each camera in an initial state of the device,
• detecting deviations dX, dY of the position of the or each laser beam from the initial values X, Y during operation of the device,
• generating a signal for the control device from the detected deviations dX, dY,
• forwarding the signal to the control device, which moves the welding head on the basis of the signal in such a way that the deviations dX, dY become smaller.

The change in the relative positions of the laser beams is due to the fact that the laser beams are virtually stationary on the suspension of the cantilever arm, while the cameras, which are attached to the welding head at the end of the cantilever arm, track the stretching, bending, deflection or torsion of the cantilever arm move relative to the stationary laser beams. By feeding the signal back to the control device, a closed control loop is created for tracking the welding head. The detection of the deviations, the generation of the signal and the forwarding to the control device is preferably carried out continuously, e.g. B. in "real time", or intermittently regularly or irregularly, preferably with the help of a process computer.

The welding head can be attached so that it can be displaced in at least two spatial directions, for example vertically and horizontally. Advantageously, it can be displaced in three spatial directions, for example additionally along or parallel to the axis of the cantilever. It is particularly advantageous if the welding head is also rotatably mounted, e.g. along or parallel to the axis of the cantilever arm, namely when when torsion of the cantilever is detected. Horizontal and vertical displacements are expressed in linear relative changes in the positions dX and dY of a laser beam, while torsional displacements produce curved deviations dX and dY, respectively.

In principle, the invention works with only one laser and only one camera. In particular, however, if twisting or torsion is also to be detected, a number of lasers and a number of cameras are required for this.

Two lasers, also referred to as laser transmitters or laser pointers, and two cameras are preferably present. As a result, horizontal and vertical displacements of the cantilever caused by torsion can be better resolved. Further camera-laser pairs would further improve the resolution.

The or each camera is preferably a matrix camera. Due to the pixel-precise imaging of the laser beam, a change in the position of the laser beam can be resolved and calculated with pixel precision.

It is particularly advantageous if a projection surface, preferably a transparently colored plate, particularly preferably a transparent white-colored plate, is arranged in the beam path between the laser and the camera. On such a projection surface, the laser beam can be better recognized and tracked by the cameras as a colored dot.

Additional data or measured values from sensors, such as a height sensor on the welding head (stick-out control) or a laser seam tracking sensor (weld seam tracking) would further improve the compensation for the effects of the cantilever arm or the tracking of the welding head. Initial values of the welding head position are preferably also recorded in an initial state of the device. In the initial state, the device is "cold", ie it is at ambient temperature.

The invention achieves a reduction in welding errors, e.g. "seam alignment" or "undercut", which are caused, among other things, by inaccurate or even undefined welding head positioning. In addition, influencing factors from the operation of the device are reduced, which improves the reproducibility of the welds and their quality. In the case of state-of-the-art internal welding systems, the welding head position must be checked by the operating personnel in the event of deflection and twisting and, if necessary, re-referenced. The compensation system according to the invention achieves a significant improvement in the reproducibility of the welding process overall, which is reflected in improved weld seam quality, weld seam geometry and a lower frequency of defects.

• Fig. 1 als Prinzipskizze eine mögliche Ausgestaltung der erfindungsgemäßen Vorrichtung in einer Draufsicht und einer Seitenansicht.

Further features and details of the invention result from the patent claims and the following description of the exemplary embodiment of the invention shown in the drawing. It shows

• 1 as a schematic diagram of a possible embodiment of the device according to the invention in a plan view and a side view.

In the device 1 shown, a cantilever arm 2 is attached to a suspension 3 . The tube or profile to be welded is not shown because it is not necessary for understanding the invention. However, the device 1 can be imagined as being in the middle of a tube or profile. A deflection of the cantilever 2 as a result of magnetism or the effects of temperature is indicated by the dashed lines 2a. In the top view in the horizontal direction, in the side view in the vertical direction. At the end of the cantilever 2, a welding head 4 is slidably mounted in the vertical and horizontal directions perpendicular to the axis of the cantilever 3, the welding head 4 itself not being shown. Two lasers 5 are attached to the suspension 3 . the respective Laser beams 5a are aimed at two cameras 6 which are attached to the end of the cantilever arm 3. In the beam path between the laser 5 and the camera 6, a transparent, preferably white, colored plate 7 is attached, it being possible, of course, for one plate 7 to be present for each pair of laser cameras. The plate 7 serves as a projection surface for the laser beams 2a, so that they can be easily recognized by the cameras 6 as a point 7a and their relative positions in the horizontal X and vertical X directions can be tracked. The deviations dX and dY are calculated from the different positions. Using a processor (not shown) and corresponding software, together an evaluation module, a signal is generated from the deviations and fed back to the control unit (also not shown). This in turn controls displacement devices 8 (vertical) and 9 (horizontal), which track the welding head 4 in such a way that the deviations dX and dY become smaller or, ideally, disappear. A laser beam point 7a can be seen in the plate 7 that has been drawn out, which, seen from the camera 6, has deviated from a position X, Y to a position X+dX, Y+dY as a result of the deflection 2a.

In the example shown, the length of the cantilever 2 is given as 30 m. This is not to be understood as a limitation, but is only intended to give an idea of the possible orders of magnitude. Of course, the lengths can be both shorter and longer. A possible torsion is not indicated in this drawing.

Reference list:

1

internal welding device

2

cantilever
2a Deflection of the cantilever

3

suspension

4

welding head

5

Laser
5a laser beam

6

camera

7

projection surface

8th

Shifting device vertical

9

Shifting device horizontal

Claims (10)

1. Device (1) for internal welding of tubes and sections, comprising a cantilever arm (2, 2a) which is secured to a suspension (3) and introducible into the tube or section to be welded and on which a welding head (4) is mounted to be displaceable, wherein the cantilever arm (2, 2a) further comprises a laser (5) and a camera (6), characterised in that

   - a control device for displacing the welding head (4) is present,

   - one or more lasers (5) are mounted on the suspension (3),

   - one or more cameras (6) are mounted on the welding head,

   - wherein one or more laser beams (5a) are each directed to the one or more cameras (6) and are recognisable by this or these,

   - an evaluating module is present, which can evaluate changes (dX, dY) of the relative positions (X, Y) of the laser beams (5a) recognised by the one or more cameras (6), generate a signal therefrom and feed this to the control device for displacement of the welding head (4).
2. Device according to claim 1, characterised in that two lasers (5) and two cameras (6) are mounted.
3. Device according to claim 1 or 2, characterised in that the or each camera (6) is a matrix camera.
4. Device according to one or more of claims 1 to 3, characterised in that a projection area (7) is arranged in the beam path between the one or more lasers (5) and the one or more cameras (6).
5. Device according to claim 4, characterised in that the projections area (7) is a transparent coloured plate.
6. Device according to one of more of claims 1 to 5, characterised in that additional sensors are present and are connected with the evaluating module.
7. Device according to claim 6, characterised in that at least one of the additional sensors is a height sensor.
8. Method of displacing a welding head (4) in a device (1) according to one or more of claims 1 to 7, comprising at least the following steps:

   - detecting start values (X, Y) of the position of the or each laser beam (5a) by the or each camera (6) in a start state of the device (1),

   - detecting departures (dX, dY) of the position of the or each laser beam (5a) from the start values (X, Y) during operation of the device (1),

   - generating a signal for the control device from the detected deviations (dX, dY),

   - passing on the signal to the control device, which so displaces (8, 9) the welding head (4) on the basis of the signal that the deviations (dX, dY) become smaller.
9. Method according to claim 8, characterised in that additional measurement values or data from additional sensors are used for generating the signal.
10. Method according to claim 8 or 9, characterised by

    - detecting start values of the welding head position in a start state of the device (1).

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